1. Field of the Invention
The present invention relates to a refrigeration circuit having multiple compressors arranged in series. More particularly, the present invention concerns a by-pass arrangement for circuiting refrigerant around a compressor and an apparatus for providing a liquid refrigerant quench to cool gaseous refrigerant between the compressors.
2. Description of the Prior Art
In a typical vapor compression refrigeration system various components such as a compressor, condenser, evaporator and expansion device are arranged to transfer heat energy between a fluid in heat transfer relation with the evaporator and a fluid in heat transfer relation with the condenser. In a heat pump system an outdoor coil and indoor coil are located such that the compressor, through a reversing valve, may direct hot gaseous refrigerant to either coil acting as a condenser. The other coil then acts as an evaporator such that depending upon the position of the reversing valve, heat energy is rejected or absorbed in both the indoor coil or the outdoor coil. In the heating mode of operation, heat is rejected in the indoor coil acting as a condenser and heat is absorbed in the outdoor coil acting as an evaporator. The reverse is true in the cooling mode of operation wherein the heat is rejected in the outdoor coil acting as a condenser and the heat is absorbed in the indoor coil acting as an evaporator.
It has been found that in air source heat pump applications that the capacity of the heat pump to provide heat energy diminishes as the ambient air temperature drops. Consequently, as the heating load is increasing, the capability of the heat pump to supply heat energy decreases. Many attempts have been made to increase the heating capacity of heat pump system at lower temperatures. One of these methods is by providing two compressors in series such that the heating capacity of the refrigeration circuit may be substantially increased at lower ambient temperatures.
When two compressors are placed in series such that there is a low stage compressor having a compressor discharge line connected to the suction line of a high stage compressor several potential problems are created. One of these problems is how to operate the system with only one compressor when ambient conditions are such that it is only necessary to operate one compressor. Another problem is how to avoid excessive refrigeration temperatures which may result in degradation of the refrigerant and/or oil mixed with the refrigerant. This present application concerns a method and apparatus of addressing these two problems.
A by-pass line is described herein for circuiting refrigerant around a low stage compressor to the suction line of a high stage compressor. This line has a check valve located therein such that when the low stage compressor is operating refrigerant may not flow from the low stage compressor discharge line to the low stage compressor suction line.
This application also discloses a quench conduit for conducting liquid refrigerant from the heat exchanger serving as the condenser to the high stage compressor suction line. This quench conduit has a control device such as a thermal expansion valve for regulating the flow of liquid refrigerant therethrough. This expansion valve meters liquid refrigerant into the high stage compressor suction line such that the liquid refrigerant flashes cooling the mixture of gaseous refrigerant being supplied to the high stage compressor.